1. Field of the Invention
The present invention relates to a terminal device capable of capturing a shot image and, in particular, relates to a terminal device which detects motions of a subject inside the shot image to execute unique control allocated to each of the motions.
2. Description of the Related Art
High integration of electronic circuits has reduced the size and weight of a terminal device, thus resulting in a difficulty of securing a sufficient space for installing input operation units such as a keyboard and a mouse. Thus, there is a case where a user is obliged to perform a complicated input operation. An interface for detecting motions of the hand and fingers has been developed as an intuitive input operation unit in place of a keyboard or a mouse.
Patent Document 1 has disclosed a technology by which edge lines of a hand are extracted from an image picked-up by a camera and subjected to Hough transform, thereby detecting directions of fingers.
Patent Document 2 has disclosed a technology by which a circumscribed rectangle of a region included in a domain of the skin color of a hand is determined and subjected to Hough transform with respect to its entirety, thereby detecting straight lines which can be candidates of the fingers.
Patent Document 3 has disclosed a technology by which a hand region is extracted on the basis of body temperatures by referring to an image obtained by using an infrared camera, thereby identifying the ends of fingers by matching the thus extracted hand region to a predetermined pattern.
Patent Document 4 has disclosed a technology by which a finger sack having three color markers, that is, red, blue and yellow, is fitted to a finger of a user and shot by using a camera, and the markers are detected by referring to this shot image, thereby distinguishing motions of the finger.    Patent Document 1: Japanese Published Patent Application No. H6-20055    Patent Document 2: Japanese Published Patent Application No. H9-35066    Patent Document 3: Japanese Published Patent Application No. 2001-282456    Patent Document 4: Japanese Published Patent Application No. 2002-269567
In the Patent Documents 1, 2, since Hough transform greater in the amount of calculations for detecting straight lines is utilized, a terminal lower in processing capability such as a cellular phone is reduced in speed of executing an application to be operated, which is a problem. Further, an image of a finger is not always constituted only with straight lines but includes many curved lines on joints and wrinkles, thereby the finger cannot be detected with high accuracy only by detecting the straight lines. Still further, there is made no description about how to discriminate straight lines on the background from straight lines on the finger.
In the Patent Document 3, an infrared camera is used for shooting an image. However, an infrared camera has not become prevalent as a camera built inside a terminal device. The infrared camera must be, therefore, assembled additionally to increase electric power consumption due to the addition, which is another problem.
In the Patent Document 4, no special sensor is needed and a generally used camera can be only used to provide an intuitive operation. However, on every operation, a finger sack must be fitted, which is troublesome.